Drying in pharmaceutical manufacturing is the removal of water and other liquid solvents from the granules or other materials by heat and a current of air. Fluidized bed dryer is used to dry the granules in pharmaceuticals using FBD finger bags.

The principle of Fluidized Bed Dryer (FBD):

1. In fluidized bed dryer, hot air is passed at high pressure through a perforated bottom of the container containing granules to be dried.

2. The granules are lifted from the bottom and suspended in the stream of air this condition is called fluidized state.

3. The hot air is surrounding every granule and dries them completely. Therefore, the granules dry equally.

Construction:

The dryer is generally made up of stainless steel. A removable bowl is attached at the base of the dryer that is used for loading and unloading of material. The stainless steel bowl has a perforated base of a wire mesh supporting for material that is being dried. A fan is available at the top of the circulating hot air. Fresh air enters; filters and heat exchange are connected serially to heat the air to the required temperature.

Working:

1. The wet granules to be dried are placed in a removable bowl. The bowl is pushed into the fluidized bed dryer.

2. Fresh air passes through the pre-filter, which subsequently get heated by passing through a heat exchange.

3. The hot air flows through the bottom of the bowl simultaneously fan is allowed to rotate.

4. The air velocity is increased with time. When the velocity of the air is more than the settling velocity of the granules, the granule remains partially suspended in the air stream.

5. After some time, a point of pressure is reached at which frictional drag on the particles is equal to the force of gravity.

6. The granules rise in the container because of high velocity of air (1.5 to 7.5 meter per minute) and later fall back in a random boiling motion. This condition is said to be a fluidized state.The gas surrounds every granule to completely dry them.

7. The air leaves the dryer by passing through the bag filter. The entrained particles remain attached to the inner surface of the finger bags. The bag is shaken periodically to remove the attached particles.

FBD Finger Bag:

The fluidized bed dryer filter bag is made up of different type of superior quality of fabrics, as per requirement of material involving in drying.

Different types of fabrics are:

1. Antistatic

2. Polypropylene

3. Stain

The manufacturing of fluidized bed dryer filter bag depends on required factor like retention micron, static change and air permeability. Fluidized bed dryer filter bags are cost-efficient and durable, as those are manufactured according to the specification and are regularly tested to meet standard quality. FBD finger bags have finger-like structures to increase their surface area and efficiency. Drying process in FBD depends upon the MOC of the finger bags. Finger bags are constructed by a combination of antistatic polymer, nylon fabric and cotton fabric.